Our research objective is to determine the genetic control of antibody structure. The analysis of the amino acid sequence of mouse lambda chains will allow an estimate of the number of germ-line genes coding for the structure of these proteins and will lead to an understanding of the origin of antibody diversity. Genetic analysis of loci that control immune responses to certain antigens may provide an estimate of the number of heavy chain variable region genes and the distance between heavy chain variable regions and constant region genes. The variable regions of myeloma antibodies and normal antibodies of restricted heterogeneity with similar specificities will be sequenced. Comparisons of these sequences will demonstrate the effect of amino acid replacements on antibody specificity.